DESCRIPTION: Cystic fibrosis is the most common lethal hereditary disease in the US and is caused by mutations in the gene encoding the CFTR chloride channel. The studies proposed herein are designed to further understanding of the molecular basis of CFTR Cl-channel function and the mechanism by which mutations that cause CF lead to channel dysfunction. CFTR activity is controlled by direct interaction of ATP with the nucleotide binding folds (NBFs) on the CFTR polypeptide, but the mechanism by which this interaction leads to channel gating is not understood. The principal aim of this research is therefore to elucidate the role of nucleotide binding and hydrolysis in gating CFTR. Five specific aims are proposed. They are: (1) to define the roles of NBF1 and NBF2; (2) to define the roles of endogenous sulfhydryls in controlling the activities of the NBFs, and the coupling thereof to channel gating; (3) to obtain biochemically pure, native, reconstituted CFTR suitable for biochemical investigations; (4) to determine the affinity and rate constants for ATP binding to and hydrolysis by purified native CFTR and to correlate ATP binding and hydrolysis kinetics with biophysical properties controlling channel gating and (5) to determine the mechanism by which CF-causing mutations, particularly those mapping to NBFs and R domain affect CFTR gating.